With each successive semiconductor technology generation, wafer diameters tend to increase and transistor sizes decrease, resulting in the need for an ever higher degree of accuracy and repeatability in substrate processing. Semiconductor substrate materials, such as silicon wafers, are routinely processed using plasma in vacuum chambers. Plasma processing techniques include sputter deposition, plasma-enhanced chemical vapor deposition (PECVD), resist strip, and plasma etch.
In a plasma processing chamber, process gas is excited into a plasma in a proximity of a substrate being processed. However, gas at other locations (such as gas holes, conduits, lift pin holes, plenums, and the like) in the plasma processing chamber can also be excited into an unwanted plasma under certain conditions. Such an unwanted plasma is called parasitic plasma. Parasitic plasma can occur in a plasma processing chamber due to many reasons, such as geometry of chamber components, gas pressure and gas chemistry used in plasma processing recipes, supply of radio frequency (RF) power, etc. Parasitic plasma can cause a variety of issues in plasma processing, such as particle contamination, spatial and temporal nonuniformity during processing, and/or premature failure of chamber components. It is therefore desirable to eliminate parasitic plasma in a plasma processing chamber.